Liberating cut-off-valve gear.



N. W. TWISS.

LIBERATING GUT-OFP VALVE GEAR.

.APPLIUATION I'ILED SEPT. 17, 1908.

1,006,808. Patented 1101.211911.

3 SHEETSwSHEET l.

COLUMBIA PLANOGRAPH Co.. WASHING c.

N. W. TWISS.

LIBBRATING GUT-OFF VALVE GEAR.

APPLICATION FILED SEPT. 17, 1908. 1,006,808.

Patented Oct. 24, 1911.

3 SHEETS-SHEET 2.

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COLUMBIA PLANosRAPH co..wAsmNG1-0N n.1.:

N. W. TWISS.

LIBBRATING GUT-OFF VALVE GEAR.

APPLICATION FILED SEPT. 17, 190B.

Patented Oct. 24, 1911.

3 SHEETS-SHEET 3.

gnuenl'oz [5077 WJz/zkx 5237i tn @web @Nini NELSON W. TWISS, OF NEWHAVEN, CONNECTICUT.

LIBERATING GUT-OFF-VALVE GEAR.

Specification of Letters Patent.

Patented. Oct.' 24, 1011.

Application filed September 17, 1908. Serial No. 453,528.

To all whom 'it may concern:

Be it known that I, NnLsoN W. Twrss, a

citizen of the United States, and resident of New Haven, in the countyof New Haven and State of Connecticut, have invented certain new anduseful Improvements in Liberating Cut-Off-Valve Gear, of which thefollowing is a full, clear, and exact speciiication.

My invention relates to an improvement 1n liberating cut-off valve gearfor steam engines of the class in which separate valves are employed forthe various valve functions, as in the well known Corliss system.

The invention has for its object to provide improved spring closing andair cushioning out oif valve mechanism, and it consists in the novelcombination, arrangement and construction of parts as hereinafter morefully described and claimed.

In the accompanying drawings forming a part of this specification,Figure l is a front elevation of a steam cylinder of the Corliss type,and valve gearing embodying my improvements, the valve spring and itscase being removed from one of the steam valves to show remaining parts.Fig. 2 is a central horizontal longitudinal section through one of thecut off or steam valve gears on line 2 2, Fig. l. Fig. 3 is aperspective view of one of the cut oif valve gears showing the cut offmechanism in the act of liberating from the driving mechanism. Fig. t isa vertical cross section on line 4 4, Fig. 2 viewed from the cylinderend of the mechanism. Fig. 5 is a similar view of a vertical crosssection on the line 5 5, of Fig. 2. Figs. 6 and 7 are cross sectionalviews on the line 6 7, Fig. 2, showing the bell crank respectively atthe extreme limits of the throw7 with the position of the steam valvecrank indicated by dotted lines.

Referring 4to the dra-wings, the arrangement of the valves with myimproved valve gearing will be recognized as that of the well knownCorliss system, in which the separate induction valves are seated at therespective ends of the cylinder on the upper side thereof, and theexhaust valves are similarly and separately placed at the lower side ofthe cylinder. The valves proper are of the regular Corliss type, hererequiring no description, seated in cylindrical valve seats in the steamand exhaust chambers in which they are adapted to be oscillated by valvestems A, A1 journaled in the bonnets I), D1, and stuffing boxes B of thebonnets, which form steam tight joints around the valve stems where theyenter the steam chambers. The exhaust valve cranks a2 are secured uponthe outer ends of the stems Al of the exhaust valves, and connectedtogether by the rod as, which is driven in the ordinary manner by therod a4, connecting the forward crank with the engine eccentric, here notrequiring to be shown. By means of a similar eccentric driven rod b1 thebell cranks of the steam valve gear are oscillated, both being connectedtogether similarly to the exhaust valve cranks by a rod a5. Thesefeatures of the valve gear are old and require no more extendeddescription.

The steam bonnets D, bolted to the upper part of the cylinder, are ofthe skeleton construct-ion required to receive the stuffing boxes Baround the valve stems adjacent to the cylinder, and are each formedwith. a cylindrical extension or sleeve E, external to the skeletonpart. The steam valve stems A are journaled in and project out throughthe bearings in the sleeves from the valves o, and have the steam valvecranks g keyed upon them contiguous to the ends of the sleeves by meansof keys as.

Upon the sleeves E, the bell cranks of the steam valve gear arejournaled, each comprising the depending lever F, to which the rod a5 isconnected, and the lever a6 on which the depending hook a7 is pivoted.The hook is adapted .to engage with the pin c1 vprojecting from the endof the steam valve crank into the plane of oscillation of the hook. Theengaging surfaces of these parts are preferably formed by hardenedshoulders or catch blocks c2, e3 respectively attached to the arm andhook as shown. A

trip arm h is secured to the hook, projecting toward the sleeve E intothe path of a cam lo on a cam lever e4, which is journaled on a hub c5on the bell crank. A spring e secured to the lever a6 and bearing on thelower side of the trip arm normally presses the hook into engagementwith the steam. valve crank pin c1, and the disengagement of said partsin the cut olf action is effected by engagement of the trip arm with thecam in the normal oscillation of the bell crank on the sleeve E.

Fig. 3 shows the trip arm in engagement with the cam, and the hook inthe act of releasing the shoulder c2 of the pin c1. In

the operation of the mechanism, the point at which the hook engages thearm el and thereby connects the steam crank g with the eccentric drivenbell crank, is the extremity of the downward oscillation of the hook,which position is shown in Fig. 6. The disengagement of the parts takesplace at different points through a range of c ut off varying from zeroto about five eighths of the stroke, as determined by the position ofthe Acam 70, which is adjusted automatically to `effect such variationof the motive action through the connecting rods L, by means of thesteam engine governor, not requiring to be here shown.

The closing movement of 'the steam valve at the point of release iseffected by the resilience of a spring, through the mechanismhereinafter described, which constitutes my particular improvement, asfollows: Pivoted on the steam valve crank arm e1 adjacent to the crankis a plunger rod z', pivotally connected to a plunger il, which isfitted to travel in 'an air lcup 2, supported on a. stationary bracket3, rigidly secured upon the end of the sleeve E of `the steam bonnet D,between the steam `crank g and the cam lever e4, by means of the setscrew mi. At the bottom of the air cup is a plunger cushioning stop 31of leather or other suitable material, perforated in alinement with thepassage through an air cock 4 inserted in the bottom of the air cup. Ata yshort distance above the stop lis an orifice 5 in the wall of the aircup, and the plunger is rendered substantially air tight by means of apacking ring 0, or other suitable method.

Rigidly secured in the stationary bracket i3 is a pin a, which projectsinto a slot u1 in the steam crank g, of sufficient length to permit thethrow of the crank relative thereto. The crank is provided with a 4hubn2, bearing a ring n3 'loosely Afitted thereon., and held in place bythe pin n secured in the hub outside o'f the ring. On the end of thevalve stem A a cylindrical caseIt is rigidly secured by a set screw apassing through the solid end of Ithe case. The

' case is provided with an interior hub nu of the dia-meter of the ringn3, and a hole n4 is drilled in the end wall of the case eX- terior ktothe fhub. A spiral spring T, having the ends 1f, t1 of the wire of whichit is composed bent over parallel lto the aXis of the coil, is arrangedaround the valve stem within the case, with the ends of the coilreceived respectively upon the hub 'an and ring n3, and the ends of thewire '15, t1 respectively Ebearing upon 'the lpin n of the stationarybracket, and the case R, by insertion in said hole l11,4.

WV ith the parts thus constructed and arranged, the spring lmay vbe`given any required tension by kturning the case around upon the shaftbefore vit vis permanently secured thereon by means of the s-et screw u.Then in operation the spring will exert its tension in oppositedirections on the valve stem and stationary bracket, and instantaneouslyeffect the closing of the steam valve when it is released from the hooka7, by the operation of the mechanism hereinbefore described. In the actof closing the movement of the valve is positively arrested by thecontact of the plunger l with the leather covered bottom 4of the air cup2, after its momentum is first overcome by compression of the air belowthe orice 5, such cushioning being regulated by the air cock @4. In

the ascent of the plunger, said air passages permit the free movement ofthe parts at the slower speed then imparted to them by the engineeccentric.

In the above construction, the pin 61,

which projects from the end of the steam valve crank into the plane ofoscillation of the 'hook a7 and is engaged by the hook to impart themotion of the eccentric to 'the steam valve crank, serves as the crankpin or journal to which the plunger rod z' is confnected. This singlepart therefore serves a double purpose, and combines both of saidfunctions, which insures the utmost compactness of the parts, simplicityand light-v ness of the mechanism, economy of construction, and minimumliability of derangement. By reduction of the weight of parts, andcorresponding reduction of inertia in movement, a far higher speed ofreciprocation of the valve gearing and consequent piston speed isattainable. In this connection, the configuration, construction andarrangement of the stationary bracket is of the utmost importance. It isreceived upon the extreme outer end of the bonnet, exterior to thebearing ofthe bell crank thereon, which comprises the levers F and as,on a cylindrical bearing concentric to that of the bell crank, but inany case of suiiiciently lesser la matter of eXtreme simplicity,involving merely the slacking of its clamping screw m.

It will be seen that by journaling .the'ca-m lever e4 on the hub e5 ofthe vbell crank, 4instead o'f upon ythe bonnet itself, the bearing ofthe crank is correspondingly lengthened. This increase of the length ofthe belrl crank bearing insures stability of movement and -is highlyadvantageous, and accomplished without proportionate lengthening of thesteam bonnet.

The spring T is exterior to the steam crank and communication betweenthe spring and a stationary abutment on the end of the steam bonnetmust, therefore, be made through the steam crank. Such abutment is inthis case the stationary bracket itself, which is provided with the pinn projecting into the slot nl in the steam crank 9, to be engaged by theinner end t of the spring coil as hereinbefore explained. Thisarrangement insures the following result, namely In the closing movementof the valve by action of the spring and its arrest by air compressionbeneath the plunger l in the dash pot or air cup 2 which is supportedupon the bracket, the thrust of the spring upon the valve crank, and theresisting pressure brought to bear upon the crank are both sustained bythe stationary bracket in the form of forces of equal action andreaction in opposite directions, whereby the strains are neutral asregards the other parts of the cut-0H mechanism. Hence said forces areneutral with respect to the other parts of the mechanism and do not tendto displace the stationary bracket in the bearing upon the bonnet.Therefore, a very small clamping force is sufficient to hold it inplace, and jar and thump of parts are entirely avoided. The bracket andthe steam crank are brought nearly in the same acting plane, and thestrains on the respective parts are, therefore, exerted without materialleverage tending to rack these parts upon each other.

The use of the ring n3 movable concentric to the steam valve, andreceiving the inner or relatively rotating end of the spring coil withreference to the valve crank, is important in forming a bearing for theoscillation of the coil on the hub a2 of the crank, which otherwisewould wear, and also contact and cramp upon the hub, to the detrimentalaction of the mechanisms.

I claim as my invention: j

In liberating valve gear for steam engines, the combination of a bonnet,a valve stem having its bearing in the bonnet and projecting therefrom,a stationary bracket hung upon the end of the bonnet, a bell crankhaving its bearing on the bonnet interior and in juxtaposition to thebracket, a valve crank secured on the valve stem exterior and injuxtaposition to the bracket., a hook pivoted on the bell crank, an armcarried by the Valve crank crossing the plane of the stationary bracketfor engagement with the hook, tripping means controlled by a governorfor releasing the hook and arm, a coil spring coacting between theprojecting end of the valve stem and the stationary bracket to close thevalve after release, and a piston and air compression cylindercooperating between the arm and stationary bracket for arresting theclosing movement of the valve after release, substantially as and forthe purpose specified.

Signed by me at New Haven, Connecticut this 14th day of September 1908.

NELSON W. TWISS. Witnesses:

MAXMILLIAN J. MARQUARDT, GEORGE L. BARNES.

Copies of this patent may be obtained for ve cents each, by addressingthe Commissioner of Patents, Washington, D. G.

